Chapter 3 Ending Changed · 7:17am Oct 21st, 2013
This is an alert to my readers that I changed a significant part of Chapter 3's plotline. The part where Dash finds Twilight's massive underground lab has been changed, as well as the chapter's ending. For your convenience, here are the two changed sections of Chapter 3:
"Twilight...?" Rainbow Dash would never admit to anypony just how nervous she was right now. Slowly, she descended the staircase to Twilight's basement, and her nose was immediately assaulted by a foul odor. She could see a large assortment of bubbling potions laid out on one of the tables, along with a strange machine that was making random beeping noises. There were some scattered papers next to the potions, but she couldn’t get close enough to read them without the smell making her dizzy. She stumbled over to the opposite side of the room, trying to clear her head, and smacked into the wall.
The pegasus opted to lie down before she lost her balance completely, and squeezed her eyes shut, fervently wishing the room would stop spinning. When she opened them, she was surprised to see that it had, indeed, stopped spinning. She was even more surprised when the wall behind her swung open to reveal a secret passage, apparently activated by her errant flank smacking against it. She got back on her hooves, and peered down the empty passageway. Strange noises emanated from its depths, and it seemed to lead into some sort of small room.
Twilight hiccuped, staring at the deactivated robot before looking back to Rainbow Dash. “Ah definahtley did not progwam it tah do DAT!”
The alicorn started giggling again, “Hey, Rainbow Dash?”
“What?”
“Rainbow Dash!”
The pegasus raised an annoyed eyebrow. “What?!”
“Rainbow Dash!” Somehow, Twilight’s voice didn’t sound like it was coming from her anymore.
“WHA— woooooooaaaaah!” All of a sudden, the world began to wobble and lose focus. Rainbow Dash tried to land, hoping solid ground would stop everything from spinning around, but there simply wasn’t any floor anymore.
“RAINBOW DASH!”
There was only darkness.
I don't like changing things I've already written, but I feel like I accidentally took the story in the wrong direction. The new, tweaked plot is much more coherent, and avoids violating the established rules of the universe, while still leaving room for plenty of absurd shenanigans. The only difference is that now the absurd shenanigans are hallucinations instead of real events.
I've taken so damn long to write this chapter I doubt anyone remembers what happened anyway 
It's very thoughtful of you to quote what you changed. And admitting your mistake is just as mature.
I don't know about the established rules of the universe (fanfiction, after all), but the changes preserve the style of your story in my opinion.